1. Field of the Invention
The present invention relates generally to hard disk drives (HDDs) and methods controlling the operation of HDDs. More particularly, the invention relates to a method of predicting and managing recording medium defects in an HDD using an approach that includes hierarchical clustering and curve fit.
2. Description of the Related Art
Documents related to the present invention include U.S. Pat. No. 7,139,145 describing a cluster-based defect detection method used during the testing for HDDs; U.S. Pat. No.6,985,319 describing a pattern-based defect identification method; and U.S. Pat. No. 7,072,129 further describing the identification of recording medium defects (i.e., as related to data sectors in a disk drive). The collective subject matter of these documents is hereby incorporated by reference. Additionally, Japanese Patent Publication No. 1995-334933 describes a method of determining the location of a scratch on a recording medium.
A HDD is one type of data storage device allowing read data to be retrieved from a disk, and write data to be recorded on the disk using one or more magnetic heads. As the data storage capacity and the data recording density of HDDs increases, and the physical size and weight of HDDs decrease, the data bit per inch (BPI) characteristic related to the data storage density in a disk rotation direction, as well as the data track per inch (TPI) characteristics related to the data storage density in a radius direction necessarily increase.
As is well understood by those skilled in the art, all practical recording media, including the magnetic surface of disks within HDDs, include defect regions in which data may not be properly recorded and/or retrieved. Hereafter, regardless of the specific type of recording media and nature (or cause) of the data storage/retrieval incapacity, such regions will be referred to as “defects”. A defect usually occurs when there is physical damage, such as a scratch, to the upper surface of a disk. Such physical damage causes a data storage/retrieval loss of at least a data byte, which is a standard unit for reading and writing data. Such defects generally cause a reduction in the overall data storage capacity of a HDD.
Accordingly, defects must be detected and accounted for (i.e., by address replacement or physical substitution, etc.) during the manufacturing process of a HDD in order to guarantee acceptable operation of the HDD in consumer use. Generally speaking, searching for (i.e., detecting) and moving to (i.e., following) a substituted normal data region for an identified defect during the read/write processes executed in a HDD is referred to as the defect management process.
Environmental changes, such as variation in temperature, humidity, and operating voltage, may cause a scratch to extend from an initially damaged region of a disk into adjacent regions. Thus, a defect area in the surface of a disk may actually increase with operation of the HDD. Accordingly, even if all “initial” defects are effectively detected and properly accounted for in a defect management process following manufacture of the HDD, “new” defects (i.e., defects arising after final manufacturing tests) may occur in relation to an existing scratch.
Unfortunately, conventional methods of detecting and/or managing defects are limited to only the initial defects, and are ill-suited to effectively deal with new defects that routinely occur proximate an initial scratch, for example.